


Unexpected Mates

by Kleineganz



Series: Unexpected Mates [1]
Category: Teen Wolf (TV)
Genre: Alpha/Beta/Omega Dynamics, Human!Stiles, Knotting, M/M, Mating, Mating Bites, Mating Bond, Only slightly underage, Soul Bond, Soulmates, Stiles Stilinski Gets Bitten, Stiles is 17, True Mates, Unexpected Relationship, alpha!Derek
Language: English
Status: Completed
Published: 2016-09-26
Updated: 2016-09-26
Packaged: 2018-08-17 12:22:25
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 3,862
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8143889
Author URL: https://archiveofourown.org/users/Kleineganz/pseuds/Kleineganz
Summary: Derek scents Stiles when they were paralyzed together at the Sheriff's office, and it sets in motion something in their biology that they cannot control.





	

**Author's Note:**

> This is my 32nd fan fiction work, but my first in the Teen Wolf fandom. I hope I captured their voices well enough (let me know if anything seems ridiculously out of character). I'm sure similar stories to this exist but this is my take on it. I hope people enjoy it!

Derek lay paralyzed on the floor of the Sherrif’s office as Stiles made a snarky remark to Matt. Seconds later Jackson, half-transformed into a Kanima, attacked and Stiles tumbled on top of him, landing like a dead weight.

“Get him off of me!” Derek growled, slightly breathless. Matt teased at what a “ _pretty good pair”_ they made, and Derek held back a growl at the very thought, trying to keep flushing with embarrassment when part of his brain agreed. Once Derek is able to draw in a deeper breath, that’s when he noticed it. Stile’s scent, under the mix of fear and uncertainty. _Mate_.

Then suddenly Stiles is being pulled off him and Matt is threatening Stile’s life with a foot on his trachea and Derek internally panics. _His mate_ is in danger and he can’t even move to save him.

Wait, no. _Mate_? Stiles can’t be his mate. That’s impossible. Stiles is human. Sure, weres can have sex with humans, but mates? No, the mating bond only happens between two weres.

Later as they lay next to each other, still paralyzed, Derek can feel the heat coming off Stiles. He still smells the human’s fear, but beneath it all, there is still the unmistakable scent of _mate_. Derek tried to put it out of his mind. Instead, he focused on trying to break the paralysis by kick-starting his body’s natural healing, while he explained to Stiles about how Matt is breaking the rules of the Kanima.

***

Everything finally came to a head, with Jackson cured of the Kanima curse and fully transformed into the werewolf he had longed to become. Gerard Argent was poisoned with mountain ash and eliminated as a threat after he was bitten. Finally, they had some peace and quiet.

After it was all over, Derek stayed as far away from Stiles as he could, as the boy finished out the school year with his friends. The last thing the human needed was a werewolf trying to mate with him. Unfortunately, Derek couldn’t stop thinking about him and he became increasingly agitated the longer he stayed away from Stiles.

Desperate, Derek finally made his way into town, to pay a visit the veterinary clinic. When he arrived just before closing he was slick with sweat and breathing heavily. Dr. Deaton came out from the back when he heard the front door open and looked shocked to see the were. “Alan, please help me,” Derek pleaded.

Alan closed the clinic and ushered Derek into the back. Derek explained as best as he could. “Why is this happening? How can a human be my mate?”

Alan was silent for a moment. “This is very rare, and I haven’t heard of a case of this in my lifetime.”

“What? What is it?” Derek pleaded.

“Stiles may still be human, but it seems he’s destined to be your mate,” Alan explained. “When you came in such close contact with him, with his scent and pheromones, it started the process in you. Your body knows that you’ve met your true mate, and now it has a need to claim. If you don’t, you could die.”

“I’ll die if I don’t claim Stiles as my mate?” Derek growled. “Stiles? Really?!”

“I’m afraid so,” Alan confirmed. “There’s no cure for this either. Stiles was born to mate with an Alpha. He must also be suffering at this point as well, and as a human, the likelihood of it being fatal is almost guaranteed. When is the last time you saw him?”

Derek shook his head, trying to recall the last time he had seen the lanky teen. “The night we killed the Kanima. When Jackson finally became a werewolf,” Derek recalled. “I’ve been avoiding Stiles since then.”

***

Stiles was in bed, groaning in pain. His entire body was slicked with sweat and he felt hot and fevered. His dad wasn’t home yet and he wasn’t sure if he needed a doctor but Stiles was pretty sure he was sick.

All of a sudden Scott burst in, a cell phone pressed to his ear. “Yeah, Dr. Deaton, Stiles is here.”

“Uhnnn, Scott, what’ya doin’ here?” Stiles mumbled as Scott reached out to feel his sweaty, fevered brow. “Yeah, he’s burning up! Should I call an ambulance? Uh-huh. Okay. You’re sure? Well, alright, but get here quick.”

Scott put his phone away and came over to lift Stiles out of bed. “Dude, I’m sorry, but Dr. Deaton said to make you take a shower to cool you down. He and Derek are going to be here soon.”

“Derek? Why’s Derek comin’?” Stiles asked.

Scott shook his head. “I dunno. Dr. Deaton said something about only Derek being able to help you now.”

Scott carried Stiles into the bathroom and stripped them both down to just their underwear before helping his friend into the shower, turning the water on and leaving it at a cool temperature. Scott got in behind him and helped Stiles to remain standing. He shivered slightly as the cool water hit his skin. “Stay with me, buddy.”

***

Alan and Derek arrived at the Stilinski house and Derek was relieved to see that the Sheriff was not currently at home. This entire situation was going to be awkward enough without having to try and explain it to Stiles’ father.

Derek led Alan up to Stiles’ bedroom and they could hear the shower still running. “Scott? Stiles? We’re here!”

Derek ran into the bathroom just as Scott was turning off the water and he grabbed a towel to wrap Stiles in, lifting the fevered boy in his arms and carrying him back to the bed. Derek noticed that he immediately began to feel better as soon as Stiles was in his arms. Alan began to check Stiles over. “He’s in heat, which is dangerous while he remains human.”

“Wait, what?!” Scott cried out. “What do you mean remains human?”

“Look, there’s no easy way to say this,” Alan sighed. “As I was telling Derek, this is a very rare occurrence, where a human is born with the genetic compatibility to become the mate of an Alpha. When they both were close enough to scent each other a couple of months back, it kicked off the process and Stiles’ body has been changing for him to take on his role as Derek’s mate.”

Stiles seemed to come back to himself a little at Derek sat close to him and his eyes went wide when Alan said the word mate. “Wait, my role as what?”

“I’m sorry Stiles, but you and Derek must have sex, or I’m afraid you will both die,” Alan explained. “Human bodies are not designed to go into heat like this, and the death of a true mate can kill an Alpha as surely as a wolfsbane bullet can. Derek must claim and mate you, and thereby turn you as well.”

“I’m so sorry Stiles,” Derek apologized. “I…wish it didn’t have to be like this.”

“Isn’t there another way?” Scott asked, clearly distressed for his friend.

Alan shook his head. “I’m afraid not. Stiles and Derek were literally born for this,” Alan said. “It’s part of his genetic makeup. It’s extremely rare. This wouldn’t have happened unless they were uniquely compatible with each other.”

“So when you say we have to…have sex,” Stiles asked. “Is that it? Does that cure us?”

“No,” Alan said. “You will become bonded for life.”

“Derek has to bond himself to me for life?” Stiles was incredulous before he started to giggle. “You don’t even like me and now you’re stuck with me? I guess there’s some poetic justice in that.”

Derek looked at him then, his eyes burning into him with a passionate intensity. “You’re wrong about that,” Derek said quietly. “I actually do like you. More than I should. I’m dangerous, everyone around me gets hurt. That’s why I was always pushing you away.”

“Oh,” Stiles blushed. “And now?”

“And now, either I let you into my life or you die,” Derek said with a hitch in his throat as he reached out and cupped the side of Stile’s face. “I don’t want you to die. Especially if there is something I can do to save you.”

Stiles leaned into the touch as he looked up into the Alpha’s eyes and saw the sincerity there. Just then they heard the Sherrif’s car drive up. “Shit, my dad’s home!”

Quickly they got Stiles and Scott dressed and Derek hid in Stile’s closet, so that when Sheriff Stilinski came in to check on his son, he found Scott and Alan sitting next to Stiles with several textbooks strewn around the bed.

“Hey, Dad!” Stiles said nervously. “How was work?”

“It was fine,” the Sheriff said suspiciously. “What’s going on here?”

“I’m just helping the boys out with some of their biology homework,” Alan explained.

“Yeah,” Stiles nodded. “We’re almost done. Scott and I were thinking of going out afterward, I might sleep over at Scott’s tonight if that’s okay? There are leftovers in the fridge for you.”

“Alright,” the Sherriff said, still looking slightly suspicious. “Thanks for helping the boys out, Alan.”

***

A half-hour later found them at Derek’s new apartment. He’d just moved in a few days before, after he realized that he couldn’t keep living at the burnt out remains of his family home indefinitely. Derek was carrying Stiles bridal style over the threshold and Derek growled at his soon-to-be mate in warning.

“Ok, ok, not going to make a bridal joke,” Stiles giggled.

Alan and Scott had accompanied them but now all Derek wanted was some privacy. He knew what had to be done and he didn’t want an audience. As he lay Stiles onto his bed, he turned to Alan and Scott. “I think I can handle it from here.”

“Yeah, I know,” Alan said. “I just want to hear it from Stiles. Kid are you okay with this?”

“What choice do I have? It’s either this or death, right?” Stiles replied. “But yeah, I’m okay with it…with the mating part anyway. Hey, I finally get to lose my v-card!”

Stiles laughed and then turned quiet for a moment. “The part…the only part that’s bothering me is needing to be turned.”

“I’m sorry, but it’s necessary,” Alan explained. “If you don’t turn, whenever you go into heat, if Derek isn’t close by, you could die. Your body isn’t designed for it. As a were you’ll still be in distress, but there will be no threat to your life.”

Stiles nodded. “Got it. Alright then. Time to add me to your pack then, Alpha.”

Satisfied, Alan and Scott retreated. “I will be by tomorrow to check on you both.”

***

Derek stared at Stiles as he heard his door clang shut. He flicked his eyes over the boy’s youthful features, remembering how _young_ Stiles was.

For a moment they just stared at each other before Derek growled and got up to pace. “This is so frustrating. This isn’t…I never…”

“I know,” Stiles said. “But yet, here we are. So c’mon…save my life already. Whenever you’re away from me I can feel this heat start to build up again.”

Derek nodded and made his way back to the bed. “For what it’s worth, I’m sorry you’ll never get to be with Lydia now.”

Stiles left out a puff of laughter. “Dude, I was never going to be with Lydia. I knew that, but it was fun to dream.”

Derek crawled up over Stiles then, reaching out to cup the boy’s face, marveling at the smoothness of his skin. He lowered his head to brush his lips against Stiles’, taking in his mate’s scent. This time there was no smell of fear overlaying it. All Derek could smell was a mix of arousal, uncertainty and _mate_.

Derek deepened the kiss, sliding his tongue into Stiles’ mouth as he slowly lowered his body, so that Stiles could feel his growing arousal against his hip. Derek was pleased to feel Stiles’ arousal as well, as the boy arched into his touch.

Derek knelt above Stiles and frowned. “I don’t want you to freak out, but I almost forgot. When I claim you, I have to do it in my werewolf form. There are a couple of things you’re going to need to know about having sex with a werewolf, especially when a claiming and mating bond are involved.”

“Ok,” Stiles gulped. “Since I know I’m going to have to be turned, that involves biting, right?”

“Yeah,” Derek acknowledged. “Specifically I’m going to have to bite you here,” Derek said as he caressed the juncture of Stiles neck and shoulder on his right side. “Hold still when I do it, I don’t want to hurt you any more than I have to.”

Stiles gulped and nodded. “What else is there?”

“When I’m aroused in my were form, I develop a knot,” Derek started to explain. “Much like a wolf or a dog. To successfully mate, I have to tie you with my knot. That part is probably going to be as painful as the bite.”

“How…how long will we remain tied?” Stiles asked.

“I’m not sure,” Derek shrugged. “I’ve never knotted a lover before. Knotting is only for mates.”

Derek could hear Stiles' heartbeat and it seemed to speed up a bit every time he said the word _mate_. “Let’s get you out of these clothes first,” Derek suggested as he began to pull Stiles’ t-shirt up. The boy lifted his arms obediently and let Derek remove it.

The Alpha then climbed off Stiles and helped him remove his jeans and underwear, noting how Stiles blushed a deep red when his arousal was exposed. Derek removed all of his own clothing as well before lying back down next to Stiles. “You’re beautiful,” Derek breathed as he captured the Stiles’ mouth again, kissing him breathless while running his hands over every bit of heated skin he could touch.

Stiles was a little more nervous now and Derek continued to caress him, pulling him closer so their erections could slide together. Stiles groaned at the contact and Derek began to kiss and lick along Stiles’ neck, sucking the skin and breathing in Stiles’ scent. Stiles seemed to instinctually arch his neck to give the Alpha better access. “Mmm good boy,” Derek praised as he continued to kiss and suck Stiles’ skin.

Once Stiles was completely boneless in his arms, Derek pulled back to look into the boy’s lust blown eyes. After kissing his lips thoroughly one more time Derek pulled back and reached for the table next to the bed to grab the bottle of lube that sat there.

“Get on your hands and knees for me sweetheart,” Derek instructed. “I need to prep you first. I don’t want any of this to hurt any more than necessary.”

Stiles shifted and got onto his hands and knees, burying his face in his arms. A mix of arousal and embarrassment was coming off of Stiles in waves now and Derek chuckled as he coated his fingers with lube and began to slowly caress Stiles’ anus. The boy moaned at the touch. “Have you ever touched yourself back here?” Derek queried as he slowly began to work a finger into the tight sphincter.

Stiles shook his head. “No…no I haven’t. I never thought I’d…be doing this.”

Derek stroked his other hand soothingly up and down Stiles’ thigh as he kept working one finger in and out of the boy’s hole. “Always thought you’d hook up with a girl, right?”

“Yeah,” Stiles started to chuckle, but it turned into a loan moan as Derek’s finger was fully inserted inside him now. “Oh fuck that feels…weird. Good weird, but still…weird.”

Derek began to slowly slide his finger in and out as he crooked it and shifted until he found Stiles’ prostate. When he began to purposely rub along that, the boy arched into his touch. “Oh fuck…fuck…shit that feels amazing!”

“That, sweetheart, is your prostate. It’s the male g-spot,” Derek explained as he continued to stimulate Stiles, spiking the boy’s arousal. “I’m going to put two fingers in now. Try and relax for me.”

Stiles did his best to relax as the second finger breached him and he felt the burn of the stretch. The burn eventually faded into a feeling of pure pleasure and as soon as Derek sensed that, he added a third finger, and eventually a fourth. Stiles was going to get his virgin ass knotted on an Alpha cock tonight and he needed all the preparation he could get.

Soon Stiles was moaning and writhing, pushing back into Derek’s thrusting fingers.

“Alright, I think you’re ready for me,” Derek said. “I’m going to fuck you now. I’ll stay human as long as possible, okay?”

Stiles just moaned incoherently and Derek chuckled again as he slicked up his length and poised himself at the boy’s entrance, holding his hips firmly. “I never thought I’d get to do this. You do have such a beautiful ass, sweetheart.”

Derek slowly began to slide his cock into Stiles’ stretched hole. Every time Stiles clenched Derek would stop and allow the boy time to adjust. Even with all the prep, Derek’s human cock was quite large, and it would only get larger once he transformed.

Finally, Derek was fully inside Stiles. “You feel amazing baby,” Derek moaned, bending over to pepper Stiles’ back with kisses. “You’re taking me so well. Your virgin ass is so tight.”

“M’not a virgin anymore,” Stiles groaned, with a smile on his face.

Derek began to slowly slide in and out and he chuckled again. “No baby. You’re not a virgin anymore.”

Derek rose up and gripped Stiles’ hips firmly as he began to thrust harder. “Fuck, sweetheart, I’m not going to last long. I have to transform soon.”

“Ok, ‘m ready,” Stiles mumbled as he continued to moan in pleasure. “Feels so good D’rek.”

“Remember, when I transform, my dick is going to get bigger,” Derek reminded Stiles as he continued to rut inside the teen.

Derek was close and he couldn’t wait any longer, so he slowed his thrusting and allowed his wolf to come to the fore as he lett the transformation take hold. Stiles keened as the cock inside of him slowly grew in length and girth. Derek growled but still had enough wherewithal to add more lube before he leaned forward. Derek placed his clawed hands on the bed on either side of Stiles’ shoulders and began to tentatively lick the spot he would soon bite to place the mating mark.

Stiles bared his neck for the wolf, knowing what had to happen and Derek growled his approval of the submissive gesture. Then, Derek began to thrust in earnest, rabbiting in and out of Stiles like the wild beast that he now was. His knot had already begun to form and was catching on Stiles’ sore and stretched hole.

“Relax,” Derek growled, his voice deep and rough. “I’m going to knot you now.”

Derek began to pound into the boy until his knot finally slipped past that tight outer ring of muscle and tied them together, causing Stiles to cry out. Once the knot was fully inside, Derek continued to thrust shallowly, dragging his knot across Stiles’ prostate. “Cum for me, cum on my knot,” Derek ordered.

Stiles was pushing his hips back, angling them trying to get the right friction against his prostate. He was close, so close. Derek could smell it on him. It took several more thrusts against his prostate and then Stiles cried out, cumming untouched, and shuddering beneath Derek’s onslaught.

Derek kissed the spot he was about to bite, praising his mate. “That’s perfect baby. You’re so perfect for me.” Then Derek growled out his own release just before he sank his fangs into Stile’s neck, just holding his mate there with his teeth as he began to release copious amounts of cum inside Stiles, his own senses whiting out at the onslaught of pleasure.

Once Derek came back to himself and released Stiles from his fangs, Stiles was whimpering. The werewolf gently maneuvered them so that they both lay on their sides, still tied together.

Stiles drifted on a wave of euphoria for a while after that, feeling safe and secure in his Alpha’s arms. He woke up sometime later with Derek gently licking the mating mark. “Did it…work?” Stiles asked groggily. “Why hasn’t the bite healed?”

“Yeah, it worked,” Derek growled, still transformed. “You already smell more like a were, my sweet mate. It’s the bite of an Alpha so it just takes longer to heal.”

Stiles snuggled closer to Derek. “I don’t know why, but I love hearing you call me _mate_ ,” Stiles said, and he felt how pleased Derek was to hear that. “Wait why am I feeling that?”

“It’s the bond sweetheart,” Derek explained. “Were bonded together now, for life. The bond allows us to sense each other better. It should grow stronger with time.” Derek was flooded with the sense of happiness and security that Stiles felt then and he hugged his mate a little tighter.

They both dozed again and when they woke up next, Derek’s cock had slid out of Stiles and he had transformed back into his human form.

Stiles turned and looked at Derek, studying his mate’s face, reaching out to stroke and caress the smooth skin and rough stubble. The feelings of love and caring that flowed between them now was so strong it brought tears to the boy’s eyes.

Derek blinked as he began to wake. “Hey, don’t cry,” Derek cooed as he reached out to pull Stiles into an embrace. “I know it’s all a bit overwhelming at first.”

Stiles nodded as he ducked his head under Derek’s chin. “I…just can’t believe it. You love me, don’t you?”

“Yeah, I do baby,” Derek confessed. “I have for a while now.”

“Why didn’t you ever say anything?” Stiles asked.

“Would you have believed me?” Derek replied.

Stiles thought about it chuckled. “No, I guess not.”

Derek pulled back so he could look Stiles in the face. “I love you, Stiles Stilinski,” the Alpha said with all sincerity.

Stiles felt it so strongly and he realized he was very quickly falling for Derek. “Yeah, I think I’m gonna fall for you hard.”

“I hope so,” Derek teased. “We’re mated for life now, kiddo.”

“Shit,” Stiles said as he came to a realization. “How are we going to tell my dad?”

Derek groaned. “I think we’ll need Alan to help explain it all to him, but I think until you turn 18 next year you have to keep living with your dad. Let’s make a show of a slow courtship so that by next year maybe he’ll accept you moving in with me.”

“Yeah,” Stiles smiled. “That sounds like a good plan. It’s going to take him at least that long to warm up to the idea that I’m not just dating a guy, but big, bad _Derek Hale_.”

**Author's Note:**

> I'd love to read comments from people letting me know what you thought of this one-shot.


End file.
